A man died and a child is in hospital after both got into trouble while "boogie boarding" at a popular beach in Newquay, the coastguard said.
A woman dialled 999 at 7pm on Sunday to report that people were entering the water at Fistral Beach to try to get the pair out.
Falmouth Coastguard rescue team was mobilised, a helicopter was scrambled and the Newquay lifeboat launched.
The child was semi-conscious and the man was given CPR until the rescue helicopter landed at the beach.
Both the man and child were airlifted to the Royal Cornwall Hospital, in Treliske along with paramedics and a policeman.
The man was later pronounced dead. The child's condition is unknown this evening.
A coastguard spokesman said tonight: "It is believed that they were boogie boarding, wet suits were not being worn and the surf height was six feet."
Boogie boarding, also known as body boarding, is a form of wave-riding using a board of foam, smaller than a surfboard.